The reason I am asking this question is because the Arizal writes (Shaar Maamare Rashbi pg. 120- new version) writes that the Techelet comes from the Kineret. If so, according to the Arizal (based on msh210's answer) the Murex trunculus could not be the real Techelet.

The source for the Chilazon being in the Kineret is the Zohar, II, 48b, on parashat Terumah:

"And blue" (Shemot 25:3): Rabbi Yitzchak said: Blue [techelet] is from that fish that is in the Sea Genosar, WHICH IS THE SEA OF GALILEE, which is in the portion of Zvulon. This color is needed for the work of the tabernacle to show this color, AS IT IS WRITTEN BEFORE US.

The sea of Galilee is the same as the Kineret, which is the same as the Sea of Genosar. So it is not originally the Arizal who says this but the Zohar. This is apparently somewhat problematic, in making Zevulun's portion that of the Kineret; there does not seem to be another source for this assertion.

If this Zohar is from Rashbi, and this Rabbi Yitzchak was a contemporary of Rashbi, this would be testimony from the time that techelet was still around.

But Nebuzaradan the captain of the guard left of the poorest of the land to be vinedressers [kormim] and husbandmen [yogbim].3 'Kornim:' R. Joseph learnt: This means balsamum gatherers from the En Gedi to Ramah. Yogbim: These are those which catch hilazon4 from the promontory of Tyre as far as Haifa.5

They still had techelet in the time of Rav Yosef.

And the Rambam (Hilchot Tzitzit 2:2) claims it is found in the Dead Sea, which is saltwater. (Though apparently some claim this is a scribal error for Mediterranean Sea.)

Needless to say, there is no species that lives in all three habitats.

So, as msh210 points out in his answer, the murex is not found in the Kineret. It is found in Mediterranean, just as the gemara states.

Should this be a problem with identifying the murex with the chilazon? No, because Rabbinic literature is rife with mutually exclusive descriptions of the chilazon (and other species). (E.g. the Rambam says the blood of chilazon is black, while Rashi says it is blue.) If one were to insist on literal and simultaneous fulfillment of all of these mutually exclusive requirements, there would be no species that would fit.

One can explain away the Zohar by saying that this was a late insertion (see Chasam Sofer) or claiming it has deep mystical meaning rather than literal meaning. One can explain away the Rambam as a taut sofer. One can perhaps explain away the gemara by asserting that they were referring to a different type of species falling under the general term chilazon, snail.

To add a bit, based on the clarified question, yes, the Arizal brings it down and seems to treat it as literal. Thus, in Shaar Maamarei Rashbi, page 120, we read:

It seems to me that it is a straightforward citation of the information brought forth in the Zohar. And he gives is mystical meaning, that Kineret corresponds to the Kinor of David; and the portion of Zevulun corresponds to the ירכא שמאלא. I agree that this can be read as a statement of the metzius, followed by a mystical explanation of the significance of that metzius. Yet I think someone who is motivated could well read the entire thing as a mystical interpretation of the cited Zohar.

Personally, I don't see the need to appeal to mystical explanations. The Zohar (plausibly) contradicts the gemara. And the Arizal did not actually see the chilazon. He is interpreting the Zohar. So, even if, according to the Arizal, murex could not be the real techelet, that does not mean that we must pasken like the Arizal and the Zohar.

I understand this source is in the Zohar (it is brought down in sources) but I quoting directly from Ari so people won't claim "it is deep and mystical." Because the Ari seems to explain it as literal, so I brought him.
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Hacham GabrielDec 27 '11 at 2:31

thanks. I added a bit to my post to address this. (i also gave a link to the sefer here and in your question.)
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josh waxmanDec 27 '11 at 4:56

I never said "we must pasken like the arizal and the zohar." According to Sefardim when Maran doesn't mention something practical we refer to Arizal and follow him. Therefore, according to Sefardim it would NOT be the proper course of action to wear Techelet.
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Hacham GabrielDec 27 '11 at 4:59

Interesting. For this, I would say to consult your local Orthodox rabbi. I am not Sefardi, so I am unfamiliar with the parameters of this klal. But could the reason be that this is kabbalah as supplement to straight halacha? And then, couldn't one distinguish between the cases and posit that this is not 'something practical', since regardless the identity of the Chilazon was lost in the time of R' Yosef Karo and Arizal? Since it was not 'practical', Maran had no reason to explicitly 'pasken' like the gemara over the Zohar?
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josh waxmanDec 27 '11 at 5:34

1

This will be my last comment on this thread, because of the StackExchange recommendation to limit comments. Rabbi Yaakov Hillel might not hold of it for a million reasons. (There are dozens of good reasons, as well as rejoinders to those reasons.) But that does not mean that you can push your particular reasoning onto him as a 'most probably'. And maybe another (even Sfardi) posek will differ with him as to the reasons. Which then does not make it into obligatory for all Sefardim.
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josh waxmanDec 27 '11 at 18:33

There's a new booklet being distributed (not very widely) by someone in Bnei Brak. In the front material has a very long letter by Rav Moshe Sternbuch shlita, which argues very strongly against bnei Torah wearing Ptil Tekhelet. Some of the reasons given sound a bit surprising to me (i.e. were beyond my limited understanding); one of them was this Zohar about techeles being from the Kinneret. Rav Sternbuch learns that the Gemara is referring to some sort of dye used for other purposes, not for tzitzit. I'm working from memory because I can't remember where I put my copy of the booklet (word for the wise: that shows you something about my memory). The booklet came out toward the beginning of 5773 and the letter was dated about a year earlier.